Heart racing?

I am currently 12 weeks pregnant. From the earlier weeks I will randomly feel my heart start to beat very fast. At first I would freak out and have to focus on breathing until it would stop. It felt what I would imagine a panic attack feels like, but I've never had one. It randomly happens even if I'm not doing anything. I googled it and saw some articles saying it's normal in pregnancy but I've never actually talked to anyone who had it happen. Any one else out there had this happen?